Production of heavy metallic coatings on metallic strands



July 11, 1967 E. L. KNAPP 3,330,690

PRODUCTION OF HEAVY METALLIC COATINGS ON METALLIC STRANDS Filed Dec. 13, 1962 3 mag I6 32 37 F1g.6 Q Q I5 BY 7 h [3 {a Jay/FM F. 5 7 73 I ATTORNEYS.

United States Patent Ohio Filed Dec. 13, 1962, Ser. No. 244,407 19 Claims. (Cl. 117-114) This inventionrelates to the production of heavy metallic coatings on metallic strands. More particularly, it relates to the production of heavy aluminum coatings on wire strands. Aluminum coated wire is coming more prominently into use for a wide variety of applications and for many of these applications it is desirable to have a relatively heavy coating of aluminum on'the strand. However, it is difficult to obtain heavy aluminum coatings on carbon steel wire strands by the hot dip method because the aluminum bath is covered by a thick tough, stringy oxide skin and if an attempt is made to apply heavy coatings at high speeds, the skin or parts thereof are pulled up by the wire being coated, which results in socalled berries, ridges and other irregularities which make the wire commercially unsaleable. According to known prior art methods about the best that could be done in the way of coating weight was a weight of about 0.20 ounce of aluminum per square foot of wire surface with a coating finish that was lustrous, bright and smooth.

It is an object of the present invention to provide a method of hot dip coating of wire with aluminum such that coating weights of 0.40 ounce of aluminum per square foot of wire surface and even greater weights may be achieved with a smooth and lustrous finish to the coating, and without production of the attendant berries, ridges and other surface irregularities.

It is an object of the present invention to disrupt and break up into minute particles the oxide skin which forms on the aluminum bath so that the minute particles of oxide may pass onto the wire in the coating in a condition in which they are throughly homogenized in the molten aluminum. In this condition the oxide does not detract from the appearance or quality of the wire and a good surface finish may be achieved.

These and other objects of the invention which will be described in greater detail hereinafter are accomplished by that series of method steps and by that apparatus of which the following will describe certain exemplary embodiments.

Reference is made to the drawings forming a part hereof and in which:

FIG. 1 is a somewhat diagrammatic representation of the strand issuing from the bath producing a meniscus and showing means for applying vibratory energy to the meniscus.

FIG. 2 is a view similar to FIG. 1 showing a modification.

FIG. 3 is a view similar to FIG. 1 showing another modification.

FIG. 3a is a plan view of FIG. 3.

FIG. 4 is a view similar to FIG. 1 showing yet another modification.

FIG. 41a is a plan view of FIG. 4.

FIG. 5 is another view similar to FIG. 1 showing still another modification.

FIG. 6 is a cross-sectional view on a somewhat enlarged scale showing how oscillatory vibrations may be applied to the ring of FIG. 2.

Briefly, in the practice of the invention the strand to be coated, which will generally be a carbon steel wire, is passed upwardly through a coating bath and this may be accomplished by an apparatus such as is disclosed in the Knapp Patent No. 2,914,423 dated Nov. 24, 1959. In

the figures, the bath of molten aluminum is indicated generally at 10. According to the present invention, the strand 11 is preferably led out of the bath through a ring indicated generally at 12, which ring has a portion 13 of a material which is wetted by the molten aluminum and a portion 14 which is of a material which is not wetted by the molten aluminum. As the strand passes upwardly through the ring 12 pumping the molten aluminum up with it, the skin which is present on the surface of the bath 10 is not pumped up through the ring 12 since the wetted portion 13 of the ring 12 gives the skin a point of attachment and blocks the skin from being dragged up out of the bath.

As the strand moves upwardly out of the bath, it pulls with it the molten aluminum in the form of a meniscus 15. Naturally an oxide skin forms on the meniscus 15 as soon as the coating metal contacts the atmosphere, but this skin is a fresh, relatively thin skin which is continuously being formed and which has not had the opportunity to get tough and stringy like the skin on the surface of the bath.

According to the present invention, vibratory energy is applied to the meniscus 15 in order to break up and disrupt the skin which does form on the meniscus 15 and to homogenize the particles of this skin with the molten aluminum so that they may be pulled onto the strand in the coating 11a without producing surface defects such as have been mentioned above. The vibratory energy is applied at a frequency of from about 60 to about 500 cycles per second. Those skilled in the art will be able to correlate frequency with amplitude in such manner as to afford the proper homogenization of the oxide particles and molten aluminum to produce a smooth flow of coating metal onto the wire strand. It will be understod that excessive vibratory energy induces oscillation in the meniscus which is undesirable because it produces a roughened coating.

It is also important that the vibratory energy be applied only to the meniscus. It should not be applied to the bath itself nor to the strand being coated. In some prior art attempts to vibrate the strand or the bath, it has been found that the excessive agitation resulting in the bath creates an increased amount of scum or oxide; and additionally such agitation disturbs the surface tension both at the entrance to, and the exit from the bath, resulting in leakage and lose of coating metal. In such prior instances where vibratory energy has been utilized in an efiort to improve coating quality, the vibration has been applied to the bath as a whole and/or to the object being coated.

The vibratory enermy may be applied in a number of different ways of which some are set forth herein.

Thus, in FIG. 1 a rod-like member 16 suitably supported and connected to a source of vibratory energy, as for example a solenoid diagrammatically illustrated at 16b, may be utilized to introduce the vibratory energy into the meniscus. As shown in solid lines, the member 16 may be axially reciprocated in a horizontal plane or as shown in broken lines at 16a it may be reciprocated at some other angle.

As shown in FIG. 2, the virbatory energy may be applied to the meniscus by means of a ring 17. This ring will also be suitably supported and mounted and connected to a source of vibratory energy. This vibratory energy may be diametral as shown by the arrows 18; it may be axial as shown by the broken line arrows 19, or it may be orbital as shown by the broken line arrows 20, or it may be a'com-bination thereof.

As shown in FIG. 3, an element of fork-like configuration 21, having the arms 22 and 23 extending on opposite sides of the strand, may be pivoted as at 24 and the vibratory energy may be applied to oscillate the member 21 as indicated by the arrows 25.

As shown in FIG. 4, the ring 12 may have a portion 12a projecting upwardly out of the bath around approximately one-half the periphery of the strand and the vibrating element may take the form of a substantially semi-circular element 26 substantially complementary to the portion 12a and this element 26 may be reciprocated in a radial direction as indicated by the arrows 27, or in an axial direction as indicated by the arrows 27a. In FIGS. 4 and 4a, it will be understood that the portion 12:: is fixed or stationary while the portion 26 has the vibratory energy imparted to it. In this embodiment, the meniscus is substantially confined whereas in all the other embodiments thus far described it is open.

Under some conditions, it is desirable to supply a protective or other gas atmosphere and in FIG. the ring 12 is shown as being extended upwardly as at 28 and having an internal annular recess 29 constituting a chamber surrounding the meniscus. A suitable gas atmosphere may be supplied to the chamber 29 through a duct 30 and the vibratory energy may be applied as by means of the rod 16 as in FIG. 1 with the portion 28 having an aperture 31 through which the rod 16 may pass with clearance, while it is being axially reciprocated as indicated by the arrows 32.

It will be understood that the way in which the vibratory energy is supplied to the respective elements 16, 17, 21 and 26 is not a part of the present invention and may be accomplished in any desired way. One way in which the oscillatory energy, as indicated by the arrows 20 in FIG. 2, may be supplied is shown in FIG. 6. In this embodiment the ring 17, of a material preferably not wetted by molten aluminum, may be mounted in a member 33 in which it is held in place by means of the sleeve 34 threaded thereinto and the member 33- may be provided with an annular internal chamber 35 containing a steel ball 36. Compressed air or other gaseous medium is supplied through a passage 37 which communicates with a passage 38 arranged tangentially to the passage 35 which constitutes a ball race.

As compressed air is supplied through the passages 37 and 38 to the chamber 35, the steel ball 36 is caused to run around the inside of the passage 35, thereby producing an oscillatory vibration of the member 33 which is transmitted to the ring 17 and thence to the meniscus 15.

It is believed that by preventing the strand from pulling the tough oxide skin from the surface of the bath onto the strand, a part of the problem heretofore encountered is solved in that the skin on the meniscus or bubble formed above the ring 12 is a relatively-fresh, light oxide skin because it is beingdisrupted and broken up into minute particles almost as quickly as it has developed to any appreciable thickness. Furthermore, the vibratory energy homogenizes the broken up particles of the oxide with the molten aluminum. Thus, the very minute particles of oxide which are homogenized in the aluminum are actually coated onto the strand but in a condition in which they do not form surface defects or irregularities and in which they do not detract in any way from the quality of the coating.

It has been found that when the meniscus or bubble is subjected to vibratory energy as described herein, very much heavier coatings of aluminum can be achieved than heretofore. Applicant has in practice achieved coatings as heavy as 0.40 ounce of aluminum per square foot of wire surface and it is anticipated that even heavier coatings may be achieved.

It will be clear that the foregoing description has been by way of example only and no restrictions other than those specifically set forth are intended.

What is claimed is:

1. In the hot dip coating of a metallic strand with a molten coating metal, wherein the strand, as it emerges from the molten coating metal, pulls with it a meniscus of molten coating metal which is covered with an oxide skin, the step of continuously disrupting said oxide skin and causing the disrupted particles of said skin to be homogenized with the molten coating metal in said meniscus, by applying vibratory energy to said meniscus, said vibratory energy being applied by means of a vibrating element in physical contact only with said meniscus.

2. In the hot dip coating of a wire strand with a molten coating metal, wherein the strand, as it emerges from the molten coating metal, pulls with it a meniscus of molten coating metal which is covered with an oxide skin, the step of continuously disrupting said oxide skin and causing the disrupted particles of said skin to be homogenized with the molten coating metal in said meniscus, by applying vibratory energy to said meniscus, said vibratory energy being applied by means of a vibrating element in physical contact only with said meniscus.

3. In the hot dip coating of a wire strand with molten aluminum, wherein the strand, as it emerges from the molten aluminum, pulls with it a meniscus of molten aluminum which is covered with an oxide skin, the step of continuously disrupting said oxide skin and causing the disrupted particles of said skin to be homogenized with the molten aluminum in said meniscus, by applying vibratory energy to said meniscus, said vibratory energy being applied by means of a vibrating element in physical contact only with said meniscus.

4. The method of claim 3, wherein the vibratory energy is applied at a frequency of from about 60 to about 500 cycles per second.

5. The method of claim 3, wherein the strand is caused to emerge from the coating bath through a ring immersed in the bath, said ring having a portion which is wetted by the molten coating metal, whereby the oxide skin on the top of the bath is prevented from being drawn out of the bath, and the skin on the meniscus is a fresh, relatively light skin which is readily disrupted by said vibratory energy.

6. In apparatus for coating a metallic strand with molten coating metal by hot dipping, wherein the strand, as it emerges from the bath of molten coating metal, pulls with it a meniscus of said coating metal which is covered with an oxide skin, means for imparting vibratory energy to said meniscus, said means for imparting said vibratory energy comprising an element in physical contact only with said meniscus, and means for imparting vibratory energy to said element.

7. Apparatus according to claim 6, wherein said element is a rod, and said vibratory energy produces axial reciprocation of said rod.

8. Apparatus according to claim 6, wherein said element is a ring through which the coated strand passes with substantial clearance, and said vibratory energy produces diametral reciprocation of said ring.

9. Apparatus according to claim 8, wherein said vibratory energy produces axial reciprocation of said ring.

10. Apparatus according to claim 8, wherein said vibratory energy produces orbital oscillation of said ring substantially in the plane thereof.

11. Apparatus according to claim 6, wherein said element terminates in a fork-like configuration with one branch of said fork-like configuration disposed on each side of said meniscus, and said vibratory energy produces an oscillation of said element. A

12. In apparatus for coating a metallic strand with molten coating metal by hot dipping, wherein the strand, as it emerges from the bath of molten coating metal, pulls with it a meniscus of said molten coating metal, a ring immersed in said bath and having an aperture through which said strand passes with substantial clearance, said ring having a portion which is wetted by the molten coating metal, whereby the oxide skin which is formed on top of the bath is prevented from being drawn out of the bath, and the oxide skin which forms on the meniscus beyond said ring is a fresh, relatively light skin, and means for imparting vibratory energy to said meniscus to disrupt said skin and to homogenize the oxide skin particles with the molten coating metal in said meniscus, said means for imparting vibratory energy comprising an element in physical contact only with said meniscus, and means for imparting virbratory energy to said element.

13. Apparatus according to claim 12, wherein said element is a rod, and said vibratory energy produces axial reciprocation of said rod.

14. Apparatus according to claim 12, wherein said element is a ring through which the coated strand passes with substantial clearance, and said vibratory energy produces diametral reciprocation of said ring.

15. Apparatus according to claim 14, wherein said vibratory energy produces axial reciprocation of said ring.

16. Apparatus according to claim 14, wherein said vibratory energy produces orbital oscillation of said ring substantially in the plane thereof.

17. Apparatus according to claim 12, wherein said element terminates in a fork-like configuration with one branch of said fork-like configuration disposed on each side of said meniscus, and said vibratory energy produces an oscillation of said element.

18. Apparatus according to claim 12, wherein said immersed ring, over substantially one-half of its annular extent, projects from said bath, and said element is constituted by substantially a half ring complementary to the projecting portion of said immersed ring, and said vibratory energy produces radial reciprocation of said half-ring, toward and away from the projecting portion of said immersed ring.

19. Apparatus according to claim 12, wherein said immersed ring is provided with an internal annular recess constituting a chamber, above the level of the coating bath, in which said meniscus is formed, said element passing through said ring into said chamber, with clearance with respect to said ring, and means for introducing a gas atmosphere into said chamber.

References Cited UNITED STATES PATENTS 2,135,652 11/1938 Whitfield et al. 117114 2,325,126 7/1943 Giesler 117-114 2,325,156 7/ 1943 Whitfield 117--114 2,484,012 10/ 1949 Calhoun.

2,514,471 7/ 1950 Calhoun.

2,702,525 2/ 1955 Whitfield 1171 14 2,824,543 2/1958 Brown 118-72 2,900,273 8/1959 Linden 1171l4 X 2,914,423 11/1959 Knapp 117114 X 2,992,941 7/ 1961 Whitley 117-102 ALFRED L. LEAVITT, Primary Examiner. I. R. BATTEN, JR., Assistant Examiner. 

1. IN THE HOT DIP COATING OF A METALLIC STRAND WITH A MOLTEN COATING METAL, WHEREIN THE STRAND, AS IT ENERGES FROM THE MOLTEN COATING METAL, PULLS WITH IT A MENISCUS OF MOLTEN COATING METAL, WHICH IS COVERED WITH AN OXIDE SKIN, THE STEP OF CONTINUOUSLY DISRUPTING SAID OXIDE SKIN AND CAUSING THE DISTRUPTED PARTICLES OF SAID SKIN TO BE HOMOGENIZED WITH THE MOLTEN COATING METAL IN SAID MENISCUS, BY APPLYING VIBRATORY ENERGY TO SAID MENISCUS, SAID VIBRATORY ENERGY BEING APPLIED BY MEANS OF A VIBRATING ELEMENT IN PHYSICAL CONTACT ONLY WITH SAID MENISCUS. 